// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/files/memory_mapped_file.h"

#include <stddef.h>
#include <stdint.h>

#include <limits>

#include "base/files/file_path.h"
#include "base/strings/string16.h"
#include "base/threading/thread_restrictions.h"

namespace base {

MemoryMappedFile::MemoryMappedFile()
    : data_(NULL)
    , length_(0)
{
}

bool MemoryMappedFile::MapFileRegionToMemory(
    const MemoryMappedFile::Region& region,
    Access access)
{
    ThreadRestrictions::AssertIOAllowed();

    if (!file_.IsValid())
        return false;

    int flags = 0;
    uint32_t size_low = 0;
    uint32_t size_high = 0;
    switch (access) {
    case READ_ONLY:
        flags |= PAGE_READONLY;
        break;
    case READ_WRITE:
        flags |= PAGE_READWRITE;
        break;
    case READ_WRITE_EXTEND:
        flags |= PAGE_READWRITE;
        size_high = static_cast<uint32_t>(region.size >> 32);
        size_low = static_cast<uint32_t>(region.size & 0xFFFFFFFF);
        break;
    }

    file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), NULL, flags,
        size_high, size_low, NULL));
    if (!file_mapping_.IsValid())
        return false;

    LARGE_INTEGER map_start = {};
    SIZE_T map_size = 0;
    int32_t data_offset = 0;

    if (region == MemoryMappedFile::Region::kWholeFile) {
        DCHECK_NE(READ_WRITE_EXTEND, access);
        int64_t file_len = file_.GetLength();
        if (file_len <= 0 || file_len > std::numeric_limits<int32_t>::max())
            return false;
        length_ = static_cast<size_t>(file_len);
    } else {
        // The region can be arbitrarily aligned. MapViewOfFile, instead, requires
        // that the start address is aligned to the VM granularity (which is
        // typically larger than a page size, for instance 32k).
        // Also, conversely to POSIX's mmap, the |map_size| doesn't have to be
        // aligned and must be less than or equal the mapped file size.
        // We map here the outer region [|aligned_start|, |aligned_start+size|]
        // which contains |region| and then add up the |data_offset| displacement.
        int64_t aligned_start = 0;
        int64_t ignored = 0;
        CalculateVMAlignedBoundaries(
            region.offset, region.size, &aligned_start, &ignored, &data_offset);
        int64_t size = region.size + data_offset;

        // Ensure that the casts below in the MapViewOfFile call are sane.
        if (aligned_start < 0 || size < 0 || static_cast<uint64_t>(size) > std::numeric_limits<SIZE_T>::max()) {
            DLOG(ERROR) << "Region bounds are not valid for MapViewOfFile";
            return false;
        }
        map_start.QuadPart = aligned_start;
        map_size = static_cast<SIZE_T>(size);
        length_ = static_cast<size_t>(region.size);
    }

    data_ = static_cast<uint8_t*>(
        ::MapViewOfFile(file_mapping_.Get(),
            (flags & PAGE_READONLY) ? FILE_MAP_READ : FILE_MAP_WRITE,
            map_start.HighPart, map_start.LowPart, map_size));
    if (data_ == NULL)
        return false;
    data_ += data_offset;
    return true;
}

void MemoryMappedFile::CloseHandles()
{
    if (data_)
        ::UnmapViewOfFile(data_);
    if (file_mapping_.IsValid())
        file_mapping_.Close();
    if (file_.IsValid())
        file_.Close();

    data_ = NULL;
    length_ = 0;
}

} // namespace base
